Silos utilized for the storage of grains and forage conventionally utilize a plurality of vertically spaced openings in one wall of the silo to permit access to the interior of the silo, as well as for silo unloading purposes. These openings are closed by doors which are either displaceable or movable to open positions. It has also been a common practice to mount ladder rungs on the doors so as to provide a continuous ladder formed by the rungs on vertically adjacent doors. One of the problems associated with prior art silo door structures is that the doors actually support the ladder rung assemblies, with the weight of the doors being supported entirely on hinges affixed to the door frame. See, for example, U.S. Pat. No. 3,709,345. U.S. Pat. Nos. 1,130,307; 1,009,889 and 2,367,720 disclose silo doors pivotally supported on pin members extending into top and bottom cross beams forming a part of a door frame. However, none of the door structures disclosed in this prior art are supported in such a way as to effectively transmit the weight of the door, and the weight of a person stepping on ladder rungs affixed to the door, to the door frame structure. If the hinge connections rust and fail, the entire door assembly is likely to fall under a person's weight acting on ladder rungs attached to the door.
Moreover, known silo door structures are not provided with locking and sealing means capable of tightly closing the door against a door frame in such a way as to preclude the admission of air and moisture. U.S. Pat. No. 1,130,307 discloses a sealing strip around a silo door frame of the type known in the prior art.
The silo door mounting and sealing structure disclosed herein has been developed with a view towards overcoming the aforesaid problems and mounting a silo door on a ladder rung structure in such a way that the weight load of the door and of a person standing in the ladder rungs is transmitted through the ladder rung assembly to the cross beams or sills forming a portion of the door frame. Also, an improved gasketing and door locking arrangement is provided to insure the airtight closing of such a silo door assembly.